The present invention generally relates to electrochemical battery cells, and more particularly to electrochemical pellet-type battery cells that employ electrode assemblies in the form of pellets.
There are many types and configurations of electrochemical battery cells employed in a variety of applications and in both rechargeable and disposable platforms. The most popular battery cells for consumer applications, particularly high current drain applications, include alkaline cells, nickel metal hydride cells, nickel cadmium cells, and lithium ion cells. As an example, alkaline batteries based on manganese oxide cathodes are widely used for consumer applications. As device power requirements of consumer applications have increased in recent years, alkaline battery producers have sought methods for improving the high drain output of their cells while retaining a simple low cost design and method of assembly. Numerous design strategies have been proposed and implemented to address the requirement of higher capacity utilization at high drain rates.
By way of background and referring to FIG. 1, a typical primary disposable or rechargeable alkaline battery cell configuration is shown in the form of a bobbin cell 10. The cell 10 includes: a cell housing in the form of a steel can 12 defining a cylindrical inner space and interior surface, which can optionally be coated with a conductive coating; a manganese dioxide cathode 14 formed by a plurality of hollow or tubular cylindrical pellets 16 pressed in the can 12; a zinc anode 18 made of an anode gel and arranged within the hollow portion of the cylindrical pellets 16 forming the cathode 14; and a cylindrical separator 20 separating the anode 18 from the cathode 14. The ionic conductivity between the anode and the cathode is facilitated by the presence of an electrolyte, such as potassium hydroxide (KOH), which is added into the cell in a predetermined quantity.
The can 12 is closed at its bottom, and has a central circular pip 22 serving as a positive terminal for the cell. A cell closure assembly hermetically seals a top end of the can 12. The cell closure assembly comprises a negative cap 24 formed by a thin metal sheet, a current collector nail 26 attached to the negative cap 24 and disposed within the anode 18 to provide electrical contact with the anode 18, and a plastic top 28 that electrically insulates the negative cap 24 from the can 12 and separates gas spaces formed beyond the cathode and anode structures, respectively.
As illustrated in FIG. 1, the bottom of the separator 20 is typically sealed by means of a hot-melt bead 34, which is used to seal the separator 20 to a washer 33 in the cell. In another variation, the washer is omitted and only a hot-melt adhesive is used. In yet another variation, a bottom seal cup may be employed without the use of a hot-melt adhesive.
While FIG. 1 illustrates a viable alkaline battery cell configuration, there is a growing need for battery cell configurations having lower costs, more robust design characteristics, and ease of manufacturability while maintaining and continually improving current outputs and other performance parameters. This remains a significant challenge given the current trend of designing consumer electronics with ever increasing power requirements while constantly seeking to reduce product and manufacturing costs to increase profit margins.
The present invention provides an improved battery cell that, among other things, addresses these growing needs.